The Lodo Wellness Center in Denver has been selling medical marijuana for several years. But since Jan. 1, when marijuana in Colorado officially moved from underground to behind the counter, the center has also been selling legal, recreational pot.

A majority of Americans now say they support full legalization, and the trend is spreading to other states.

Meanwhile, the public health community is warning of a potential safety problem: more people driving while stoned. But health officials and law enforcement don't yet have the data or the tools to address the concern.